1. Field of the Invention
The invention relates to a composite thin film magnetic head having an inductive-type magnetic transducer for writing and a magnetoresistive element for reproducing, and a method of manufacturing the same.
2. Description of the Related Art
In recent years, performance improvement in thin film magnetic heads has been sought in accordance with an increase in surface recording density of a hard disk drive. As a thin film magnetic head, a composite thin film magnetic head has been widely used. The composite thin film magnetic head has a layered structure having a recording head with an inductive-type magnetic transducer for writing and a reproducing head with a magnetoresistive element (referred to as MR element in the followings) for reading-out. As MR elements, there are an AMR element that utilizes the anisotropic magnetoresistance effect (referred to as AMR effect in the followings) and a GMR element that utilizes the giant magnetoresistance effect (referred to as GMR effect in the followings). A reproducing head using the AMR element is called an AMR head or simply an MR head. A reproducing head using the GMR element is called a GMR head. The AMR head is used as a reproducing head whose surface recording density is more than 1 gigabit per square inch. The GMR head is used as a reproducing head whose surface recording density is more than 3 gigabit per square inch.
In general, an AMR film is a film made of a magnetic substance which exhibits the MR effect and has a single-layered structure. In contrast, many of the GMR films have a multi-layered structure consisting of a plurality of films. There are several types of producing mechanisms of the GMR effect. The layer structure of the GMR film depends on those mechanisms. The GMR films include a superlattice GMR film, a spin valve film, a granular film and so on. The spin valve film is most sufficient since the film has a relatively simple structure, exhibits a great change in resistance in a low magnetic field, and is suitable for mass production.
As a primary factor for determining the performance of a reproducing head, there is a pattern width, especially an MR height. The MR height is the length (height) between the end of an MR element closer to an air bearing surface and the other end. The MR height is originally controlled by the amount of grinding when the air bearing surface is processed. The air bearing surface (ABS) is a surface of a thin film magnetic head facing a magnetic recording medium and is also called a track surface.
Performance improvement in a recording head has also been expected in accordance with the performance improvement in a reproducing head. It is necessary to increase the track density of a magnetic recording medium in order to increase the recording density among the performance of a recording head. In order to achieve this, it is necessary to develop a recording head with a narrow track structure, the width of a bottom pole and a top pole sandwiching a write gap on the air bearing surface being reduced to the order of some microns to submicron. Semiconductor process technique is used to achieve the narrow track structure.
Another factor which determines the performance of a recording head is the throat height (TH). The throat height is the length (height) of a portion (magnetic pole portion) from the air bearing surface to an edge of an insulating layer which electrically isolates the thin film coil. Reducing the throat height is desired in order to improve the performance of a recording head. The throat height is also controlled by the amount of polishing when the air bearing surface is processed.
In order to improve the performance of a thin film magnetic head, it is important to form the recording head and the reproducing head in well balance.
Now, an example of a method of manufacturing a composite thin film magnetic head will be described with reference to FIGS. 9A, 9B to FIGS. 14A, 14B as an example of a method of manufacturing a thin film magnetic head of the related art.
As shown in FIGS. 9A and 9B, an insulating layer 102 made of, for example, alumina (aluminum oxide, Al2O3) is formed in a thickness of about 5 to 10 xcexcm on a substrate 101 made of, for example, altic (Al2O3xc2x7TiC). Then, a bottom shield layer 103 for a reproducing head made of, for example, permalloy (NiFe) is formed on the insulating layer 102.
Next, as shown in FIGS. 10A and 10B, for example, alumina of about 100-200 nm in thickness is deposited on the bottom shield layer 103 to form a shield gap film 104. Next, an MR film 105 of tens of nanometers in thickness for making up the MR element for reproducing is formed on the shield gap film 104, and photolithography with high precision is applied to obtain a desired shape. Next, a lead terminal layer 106 for the MR film 105 is formed by lift-off method. Next, a shield gap film 107 is formed on the shield gap film 104, the MR film 105 and the lead terminal layer 106, and the MR film 105 and the lead terminal layer 106 are buried in the shield gap films 104 and 107. Next, a top shield-cum-bottom pole (called bottom pole in the followings) 108 of about 3 xcexcm in thickness made of, for example, permalloy (NiFe), which is a material used for both the reproducing head and the recording head, is formed on the shield gap film 107.
Next, as shown in FIGS. 11A and 11B, a write gap layer 109 of about 200 nm in thickness made of an insulating layer such as an alumina film is formed on the bottom pole 108. Then, an opening 109a for connecting the top pole and the bottom pole is formed through patterning the write gap layer 109 by photolithography. Next, a pole tip 110 is formed of a magnetic material made of permalloy (NiFe) and nitride ferrous (FeN) through plating method, and a connecting-portion pattern 110a of the top pole and the bottom pole is formed. The bottom pole 108 and a top pole layer 116 which is to be described later are connected by the connecting-portion pattern 110a and so that forming a through hole after CMP (Chemical and Mechanical Polishing) procedure, which is to be described later, becomes easier.
Next, as shown in FIGS. 12A and 12B, the write gap layer 109 and the bottom pole 108 are etched about 0.3-0.5 xcexcm by ion milling using the pole tip 110 as a mask. By etching to the bottom pole 108 to be a trim structure, widening of effective write track width can be avoided (that is, suppressing spread of magnetic flux in the bottom pole when data is being written). Then, after an insulating layer 111 of about 3 xcexcm, made of, for example, alumina is formed all over the surface, the whole surface is planarized by CMP.
Next, as shown in FIGS. 13A and 13B a thin film coil 112 for an inductive-type recording head made of, for example, copper (Cu) is selectively formed on the insulating layer 111 by, for example, plating method. Further, a photoresist film 113 is formed in a desired pattern on the insulating layer 111 and the thin film coil 112 by photolithography with high precision. Then, a heat treatment of a predetermined temperature is applied to palanarize the photoresist film 113 and to insulate between the turns of the thin film coil 112. Likewise, a thin film coil 114 and a photoresist film 115 are formed on the photoresist film 113, and a heat treatment of a predetermined temperature is applied to planarize the photoresist film 115 and to insulate between the turns of the thin film coils 114.
Next, as shown in FIGS. 14A and 14B, a top yoke-cum-top pole layer (called a top pole layer in the followings) 116 made of, for example, permalloy, which is a magnetic material for recording heads, is formed on the top pole 110, and the photoresist films 113 and 115. The top pole layer 116 is in contact with the bottom pole 108 in a rearward position of the thin film coils 112 and 114, while being magnetically coupled to the bottom pole 108. Then, an overcoat layer 117 made of, for example, alumina is formed on the top pole layer 116. At last, a track surface (air bearing surface) 118 of the recording head and the reproducing head is formed through performing machine processing on the slider to complete a thin film magnetic head.
In FIGS. 14A and 14B, TH represents the throat height and MR-H represents the MR height, respectively. P2W represents the track (magnetic pole) width.
As an factor for determining the performance of a thin film magnetic head, there is an apex angle as represented by xcex8 in FIG. 14A besides the throat height TH and the MR height MR-H and so on. The apex angle is an angle between a line connecting the corner of a side surface of the photoresist films 113 and 115 on the track surface side and an upper surface of the top pole layer 116.
To improve the performance of a thin film magnetic head, it is important to precisely form the throat height TH, the MR height MR-H, the apex angle xcex8 and the track width P2W as shown in FIGS. 14A and 14B.
Especially in recent years, submicron measurement of 1.0 xcexcm or less is required for the track width P2W in order to make a high surface density recording possible, that is, to form a recording head with a narrow track structure. To achieve this, a technique of processing a top pole to submicron using a semiconductor processing technique is required. Also, using the magnetic materials having higher saturation flux density for the magnetic pole is desired in accordance with being a narrow track structure.
The problem is that it is difficult to minutely form the top pole layer 116 on a coil portion (apex area) which is protruded like a mountain covered with photoresist films (for example, the photoresist films 113 and 115 shown in FIG. 14A).
As a method of forming the top pole, frame plating method is used as disclosed in, for example, Japanese Patent Application laid-open in Hei 7-262519. When the top pole is formed by the frame plating method, first, a thin electrode film made of, for example, permalloy is formed all over the apex area. Next, a frame for plating is formed by applying photoresist on it, and patterning it through photolithography. Then, the top pole is formed through plating method using the electrode film formed earlier as a seed layer.
There is, for example, 7-10 xcexcm or more difference in height in the apex area described above. If the film thickness of the photoresist formed on the apex area is required to be 3 xcexcm or more, a photoresist film of 8-10 xcexcm or more in thickness is formed in the lower part of the apex area since the photoresist with liquidity gathers into a lower area. To form a narrow track as described, a pattern with submicron width is required to be formed with a photoresist film. Accordingly, it is necessary to form a micro pattern with submicron width with a photoresist film of 8-10 xcexcm or more in thickness, however, it has been extremely difficult.
During an exposure of photolithography, a light for the exposure reflects by an electrode film made of, for example, permalloy, and the photoresist is exposed also by the reflecting light causing deformation of the photoresist pattern. As a result, the top pole can not be formed in a desired shape and so on, which means, its side walls take a round shape. As described, it has been extremely difficult with the related art to precisely control the track P2W and to precisely form the top pole to have a narrow track structure.
For the reasons described above, as shown in the procedure of an example of the related art in FIGS. 11A and 11B to FIGS. 14A and 14B, a method of connecting the pole tip 110 and a yoke-cum-top pole layer 116 after forming a track width of 1.0 xcexcm or less with the pole tip 110 which is effective for forming a narrow track of a recording head, that is, a method of dividing the regular top pole into the pole tip 110 for determining the track width and the top pole layer 116 which becomes the yoke for inducing magnetic flux is employed (Ref. Japanese Patent Application laid-open Sho 62-245509, and Sho 60-10409). By dividing the top pole into two as described, the pole tip 110 can be minutely processed to submicron width on a flat surface of the write gap layer 109.
However, in this thin film magnetic head, there have still existed problems as follows.
(1) In a magnetic head of the related art, the throat height is determined by the length from the track surface 118 of the pole tip 110 to the further end. However, if the width of the pole tip 110 becomes narrower, the pattern edge is formed taking a rounded shape by photolithography. Therefore, the throat height which requires the measurement with high precision is not formed to be uniform. As a result, the track width of a magnetoresistive element and the throat height can not be formed in well balance at the time of processing the track surface and during the step of polishing. For example, if the track width requires to be 0.5 to 0.6 xcexcm, the further edge from the track surface 118 of the pole tip 110 shifts from the throat height zero position to the track surface side so that there is a large write gap. As a result, there has often occurred a problem that writing of recording data could not be performed.
(2) As described, in a magnetic head of the related art, the track width of a recording head is determined by the pole tip 110, which is one of the top pole being divided into two. Therefore, the other top pole layer 116 is not required to be processed as minute as the pole tip 110. However, the position of the top pole layer 116 over the pole tip 110 is determined by positioning of photolithography. Accordingly, if both of the top pole layer 116 and the pole tip 110 shift largely to one side when looking at them from the track surface 118 (FIG. 14A) side, so-called a side-write, which means writing is also performed in the top pole layer 116, occurs. As a result, the effective track width becomes wider and writing is also performed in a region other than the designated data recording region in a hard disk.
Furthermore, if the track width of a recording head becomes very minute, especially equal to or less than 0.5 xcexcm, the process precision with submicron width is also required in the top pole layer 116. As a result, if the difference in the sizes of the pole tip 110 and the top pole layer 116 in the lateral direction is too large when looking at them from the track surface 118 (FIG. 14A) side, as described above, a side-write occurs. That is, writing is also performed in a region other than the designated data recording region.
Accordingly, not only the pole tip 110 but also the top pole layer 116 is required to be processed to submicron. However, there has been still a large difference in height of the apex area under the top pole layer 116, as described, so that fine processing of the top pole layer 116 has been difficult.
(3) In a magnetic head of the related art, there has been another problem that it has been difficult to shorten the yoke length. The shorter the coil pitch is, the shorter the yoke length of a head becomes. Accordingly, a recording head which is excellent especially in high frequency characteristic can be formed. However, if the coil pitch becomes extremely small, the distance from the throat height zero position to the periphery end of the coil has become a primal factor for preventing the yoke length from shortening. The yoke length of a two-layered coil can be more shortened compared to that of a single-layered coil. Therefore, many of the recording heads for high frequency employ the two-layered coils.
In a magnetic head of the related art, after forming a first layer of coil, a photoresist film of about 2 xcexcm in thickness is formed as an insulating film between the turns of the coil. Therefore, a small apex area taking a round shape is formed in the periphery end of the first layer of coil. Then, a second layer of coil is to be formed thereon. However, the second layer of coil can not be formed since a seed layer of the coil can not be etched on the slope of the apex area and the coil short-circuits. Therefore, the second layer of coil is required to be formed on a flat area. If the coil is 2 to 3 xcexcm in thickness and the insulating film between the turns of the coil is 2 xcexcm in thickness and the angle of the slope of the apex area is 45 to 55xc2x0, the distance from periphery end of the coil to the area adjacent to the throat height zero position is required to be 8 to 10 xcexcm which is twice as much 4 to 5 xcexcm (the distance from the contact area of the top pole and the bottom pole to the periphery end of the coil is also required to be 4 to 5 xcexcm). This has prevented the yoke length from shortening. For example, when forming two layers of coil with eleven turns and the line/space being 1.0 xcexcm/1.0 xcexcm, the length of the coil which occupies the yoke length is 11 xcexcm provided that the first layer has six turns and the second layer has five turns. Therefore, shortening of the yoke length can not be performed further since the apex area of the periphery end of the above-mentioned coil is required to be 8 to 10 xcexcm. This has prevented the high frequency characteristic from improving.
If the yoke length of a thin film magnetic head can be shortened, the length of the coil can be shortened as well. Accordingly, the film thickness of the coil can be made thinner (e.g. from 2 to 3 xcexcm of the related art to about 1.0 to 1.5 xcexcm). Thereby, Read-Write-Distance (RWD) can be made smaller (detail will be described later), and recording and reproducing capacity can be increased. However, there has been a problem that the electrical resistance value of the coil becomes large when the thickness of the thin film coil becomes as thin as about 1.5 xcexcm.
As the related art of the invention, there are Japanese Patent Application laid-open Hei 2-132616 and Japanese Patent Application laid-open Hei 2-247811. Japanese Patent Application Hei 2-132616 discloses a technique in which the cross section of the upper coil (the second coil conductor) facing the top magnetic film is made substantially smaller than that of the lower coil (the first coil conductor) facing the bottom magnetic film. However, with this technique, RWD can not be made smaller, and recording and reproducing capacity can not be increased. Hence, precise control of the throat height of a recording head can not be achieved. On the other hand, Japanese Patent Application laid-open Hei 2-247811 discloses a technique in which the resistance value of the coil is decreased by widening the width of the upper coil than that of the lower coil. With this technique, although RWD can be made smaller, shortening the yoke length is still difficult. In addition, the above-mentioned problems such as precise control of the throat height of a recording head can not be solved, either.
The invention is designed to overcome the foregoing problems. The first object is to provide a thin film magnetic head in which: precise control of the throat height of a recording head can be performed; the yoke length can be shortened; film thickness can be made thinner without increasing the electrical resistance value of the thin film coil; and the high frequency characteristic and the surface recording density can be improved, and a method of manufacturing the same.
The second object is to provide a thin film magnetic head in which, in addition to the above-mentioned effects, not only the pole tip but also the top pole layer can be minutely processed to submicron width and the characteristic of the recording head is improved, and a method of manufacturing the same.
A thin film magnetic head of the invention includes: a magnetoresistive element; at least two magnetic layers including a first magnetic pole and a second magnetic pole, which are magnetically coupled while part of the side facing a recording medium oppose each other with a write gap layer in between; and a thin film coil with two or more layers for generating magnetic flux; wherein the thin film magnetic head comprises: a first magnetic layer formed on the side closer to the magnetoresistive element, which is one of the two magnetic layers; a first magnetic pole which is formed separately from the first magnetic layer while the opposite surface of the surface adjacent to the write gap layer is magnetically coupled to part of the region of the first magnetic layer; an insulating layer which is formed of an inorganic material and is formed extendedly at least from a surface of the first magnetic pole, which is the opposite side of a surface facing the recording medium, to one of the surface of the first magnetic layer; a first thin film coil formed with at least part of the film-thickness direction being located in the region where the insulating layer is formed; a second magnetic layer including a second magnetic pole which opposes the first magnetic pole with the write gap layer in between; and a second thin film coil with one, two or more layers with thicker film thickness than the first thin film coil, which is formed in a position more distant from the magnetoresistive element than the first thin film coil while electrically connected to the first thin film coil.
A method of manufacturing a thin film magnetic head of the invention includes the steps of: forming a first magnetic layer after forming a magnetoresistive element, and forming a first magnetic pole on the first magnetic layer to be magnetically coupled to part of the region of the first magnetic layer; forming an insulating layer made of an inorganic material at least from a surface of the first magnetic pole, which is opposite to a surface facing the recording medium, to one of the side of the first magnetic layer extendedly; forming a first thin film coil in the concave region where the insulating layer is formed; forming a second thin film coil with one, two or more layers with thicker thickness than that of the first thin film coil while electrically connecting to the first thin film coil after forming the first thin film coil; and forming a write gap layer at least on the first magnetic pole and then forming a second magnetic layer including the second magnetic pole so as to cover the second thin film coil.
In a thin film magnetic head and a method of manufacturing the same of the invention, a first magnetic pole is formed being protruded on a first magnetic pole layer and a first thin film coil is formed in a concave area adjacent to the first magnetic pole. A second thin film coil is formed thicker than the first thin film coil. Accordingly, an insulating layer made of an inorganic material can be buried in the concave area adjacent to the first magnetic pole. Thus, the throat height is precisely determined by the end of the opposite side of the track surface of the first magnetic pole.
Furthermore, by burying the thin film coil inside the concave adjacent to the first magnetic pole, the difference in height in the apex area can be decreased compared to that of the related art. As a result, in the step hereafter, the difference in thickness of the photoresist film in the top and the bottom of the apex area can be decreased when forming a second magnetic layer by photolithography. As a result, the second magnetic layer can be minutely formed to submicron measurement.
In addition, the resistance of the coil is decreased and the fist thin film coil can be formed as thin as possible since the second thin film coil is thicker than the first thin film coil. As a result, recording and reproducing capacity can be increased by making the RWD smaller and the skew angle larger.
In addition to the above-mentioned configuration, a thin film magnetic head and a method of manufacturing the same of the invention, the following condition can be applicable.
In a thin film magnetic head and a method of manufacturing the same of the invention, the second magnetic pole may be formed on the write gap layer which is formed on the first magnetic pole by dividing the second magnetic pole and the second magnetic layer. Then the second magnetic layer may be formed to be magnetically coupled to the second magnetic pole.
In a thin film magnetic head and a method of manufacturing the same of the invention, the film thickness of the second magnetic pole may be formed thicker than that of the first magnetic pole.
In a thin film magnetic head and a method of manufacturing the same of the invention, the length from the surface of the first magnetic pole opposing the recording medium may be formed equal to the throat height of a recording head. In other words, in a thin film magnetic head and a method of manufacturing the same of the invention, the first magnetic pole is separated from the first magnetic layer and is formed being protruded on the first magnetic layer. Thus, an insulating layer made of an inorganic material is formed adjacent to the first magnetic pole. As a result, the throat height is precisely determined by making the length from the surface of the first magnetic pole facing the recording medium to the inward direction equal to the throat height of the recording head.
In a thin film magnetic head and a method of manufacturing the same of the invention, a first insulating layer may be formed extendedly from a surface of the first magnetic pole, which is opposite to a surface facing the recording medium, to one of the surface of the first magnetic layer; and a second insulating layer may be formed at least in between the turns of the first thin film coil.
In a thin film magnetic head and a method of manufacturing the same of the invention, the surface of the second insulating layer which is opposite to the surface adjacent to the first magnetic layer may be planarized to be substantially the same surface as that of the first magnetic pole which is opposite to the surface adjacent to the write gap layer.
In a thin film magnetic head and a method of manufacturing the same of the invention, the width along the surface of the first magnetic pole facing the recording medium may be formed wider than that of the second magnetic pole.
Furthermore, in a thin film magnetic head and a method of manufacturing the same of the invention, the end of the surface of the second magnetic layer facing the recording medium may be formed in a rearward position of the surface facing the recording medium
In a thin film magnetic head and a method of manufacturing the same of the invention, a third insulating layer may be further formed extendedly at least from a surface of the second magnetic pole, which is opposite to a surface facing the recording medium, to the surface of the write gap layer which is opposite to the surface adjacent to the second magnetic pole.
Furthermore, in a thin film magnetic head and a method of manufacturing the same of the invention, the second thin film coil may be covered with other insulating layer than the first to the third insulating layer in between the third insulating layer and the second magnetic layer.
Moreover, in a thin film magnetic head and a method of manufacturing the same of the invention, the third insulating layer and the other insulating layer may be planarized to be substantially the same surface as that of the second magnetic pole which is opposite to the surface adjacent to the write gap layer.
Other and further objects, features and advantages of the invention will appear more fully from the following description.